U.S. patent number 10,473,536 [Application Number 15/675,269] was granted by the patent office on 2019-11-12 for gap compensation for magnetostrictive torque sensors.
This patent grant is currently assigned to Bently Nevada, LLC. The grantee listed for this patent is Bently Nevada, LLC. Invention is credited to Brian F. Howard, Dan Tho Lu, Pekka Tapani Sipila.
United States Patent |
10,473,536 |
Lu , et al. |
November 12, 2019 |
Gap compensation for magnetostrictive torque sensors
Abstract
A gap compensated torque sensing system and methods for using
the same are provided. The system can include a sensor head in
communication with a controller. The sensor head can contain a
torque sensor and a proximity sensor coupled to the sensor head.
The torque and proximity sensors can each sense magnetic fluxes
passing through the target and a gap between the sensor head and
the target. The controller can estimate torque applied to the
target from magnetic fluxes sensed by the torque sensor. The
controller can determine an improved gap measurement that is
independent of electromagnetic properties of the target from
magnetic fluxes sensed by the torque and proximity sensors. The
estimated torque can be modified by the improved gap measurement to
compensate for changes in magnetic properties of the target due to
variations in the gap. In this manner, the accuracy of the torque
measurements can be increased.
Inventors: |
Lu; Dan Tho (Minden, NV),
Howard; Brian F. (Minden, NV), Sipila; Pekka Tapani
(Garching Bei Munchen, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Bently Nevada, LLC |
Minden |
NV |
US |
|
|
Assignee: |
Bently Nevada, LLC (Minden,
NV)
|
Family
ID: |
63207615 |
Appl.
No.: |
15/675,269 |
Filed: |
August 11, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20190049320 A1 |
Feb 14, 2019 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01B
7/14 (20130101); G01V 3/10 (20130101); G01L
3/102 (20130101); G01L 1/125 (20130101); G01D
3/0365 (20130101) |
Current International
Class: |
G01L
1/00 (20060101); G01V 3/10 (20060101); G01L
1/12 (20060101) |
Field of
Search: |
;73/862.325 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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3290885 |
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Mar 2018 |
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EP |
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2012/152720 |
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Nov 2012 |
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WO |
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Other References
European Search Report for Application No. 18188243.2, dated Jan.
18, 2019 (11 pages). cited by applicant.
|
Primary Examiner: Noori; Max
Attorney, Agent or Firm: Mintz Levin Cohn Ferris Glovsky and
Popeo, P.C.
Claims
What is claimed is:
1. A magnetostrictive sensor, comprising: a sensor head including,
a driving pole having a driving coil coupled thereto that is
configured to generate magnetic fluxes in response to a driving
current; two magnetic sensors coupled to respective sensing poles
and each configured to output a first signal based at least upon
first magnetic fluxes and second magnetic fluxes sensed by the two
magnetic sensors, the first sensed magnetic fluxes resulting from
interaction of the generated magnetic fluxes with a target, a gap
between the sensor head and the target and the second sensed
magnetic fluxes resulting from interaction of the generated
magnetic fluxes with the gap; and a proximity coil coupled to the
driving pole that is configured to output a second signal based at
least upon the first magnetic fluxes, the second magnetic fluxes,
and third magnetic fluxes sensed by the proximity coil, the third
magnetic fluxes resulting from interaction of the generated
magnetic fluxes with the gap; and a controller in electrical
communication with the sensor head, the controller configured to,
receive the first signals and the second signal, determine a third
signal based upon the first signals and the second signal, wherein
the third signal is a function of the gap, and determine a force
applied to the target based upon the first signals and the third
signal.
2. The sensor of claim 1, wherein the controller is configured to
sum the first signals and determine the third signal based upon a
difference between the sum of the first signals and the second
signal.
3. The sensor of claim 2, wherein the force is a torque.
4. The sensor of claim 1, wherein the two magnetic sensors are
arranged approximately symmetrically with respect to the driving
pole.
5. The sensor of claim 1, wherein the third sensed magnetic flux is
approximately independent of electromagnetic properties of the
target.
6. The sensor of claim 1, wherein the second and third magnetic
fluxes avoid impinging the target.
7. A proximity sensing method, comprising: generating magnetic
fluxes that extend through a first region, a second region, and a
third region, the first region including a target, a pair of first
sensors, and a second sensor, the second region including the pair
of first sensors and the second sensor, and the third region
including the second sensor; measuring, by the pair of first
sensors, a combination of the first magnetic fluxes resulting from
interaction of the generated magnetic fluxes and the target and
second magnetic fluxes resulting from interaction of the generated
magnetic fluxes and a gap between the second sensor and the target;
and measuring, by the second sensor, a combination of the first
magnetic fluxes, the second magnetic fluxes, and third magnetic
fluxes, the third magnetic fluxes resulting from interaction of the
generated magnetic fluxes and the gap; wherein the second and third
magnetic fluxes avoid impinging the target.
8. The method of claim 7, further including, determining the third
magnetic fluxes based upon combination of the first and second
magnetic fluxes measured by the pair of first sensors and the
first, second, and third magnetic fluxes measured by the second
sensor; and determining the gap based upon the third magnetic
fluxes.
9. The method of claim 8, wherein the third magnetic flux is
approximately independent of electromagnetic properties of the
target.
10. The method of claim 7, wherein each of the first and second
sensors are inductive sensors configured to output a signal based
upon magnetic fields respectively extending therethrough.
11. The method of claim 7, wherein the pair of first sensors are
positioned approximately symmetrically with respect to a source of
the generated magnetic flux.
12. A sensing method, comprising: generating magnetic fluxes with a
driving coil coupled to a driving pole of a magnetostrictive torque
sensor; outputting, by two magnetic sensors coupled to respective
sensing poles of the magnetostrictive sensor, first signals based
at least upon first magnetic fluxes and second magnetic fluxes
sensed by the two magnetic sensors, the first sensed magnetic
fluxes resulting from interaction of the generated magnetic fluxes
with a target, a gap between the magnetostrictive torque sensor and
the target, and the two sensing poles and the second sensed
magnetic fluxes resulting from interaction of the generated
magnetic fluxes with the gap and the two sensing poles; and
outputting, by a proximity coil coupled to the driving pole, a
second signal based at least upon a combination of the first
magnetic fluxes, the second sensed magnetic fluxes, and third
magnetic fluxes sensed by the proximity coil, the third magnetic
fluxes resulting from interaction of the generated magnetic fluxes
with the gap; wherein the second and third magnetic fluxes avoid
impinging the target.
13. The method of claim 12, further including, determining a torque
applied to the target based upon the first signals; determining the
gap based upon the first signals and the second signal; and
adjusting the torque determined from the first signals based upon
the gap determined from the first signals and the second
signal.
14. The method of claim 13, wherein the force is a torque.
15. The sensor of claim 12, wherein the two magnetic sensors are
arranged approximately symmetrically with respect to the driving
pole.
16. The sensor of claim 12, wherein the third sensed magnetic flux
results from interaction of the generated magnetic flux with the
gap only.
Description
BACKGROUND
Sensors can be used in a variety of industries to monitor
equipment. As an example, torque sensors can be used to monitor
rotating machine components (e.g., shafts) and output signals
representative of torque applied to the monitored components. By
comparing measured torques to design specifications, it can be
determined whether monitored components are operating within these
specifications.
Magnetostrictive torque sensors are a type of sensor that employs
magnetic fields for measuring torque. In general, magnetostriction
is a property of ferromagnetic materials that characterizes changes
in shape (e.g., expansion or contraction) of the material in the
presence of a magnetic field. Conversely, magnetic properties of a
ferromagnetic material, such as permeability (the capability to
support development of a magnetic field within the material) can
change in response to torque applied to the material. A
magnetostrictive torque sensor can generate magnetic flux that
permeates a shaft and it can sense the magnetic flux as it
interacts with the shaft. As an amount of torque applied to the
shaft changes, a magnetostrictive sensor can output signals
representative of torques applied to the shaft based upon the
sensed magnetic flux.
However, the distance or gap separating a magnetic torque sensor
and a monitored component can change due to vibrations and/or
variations in shape of the monitored component during rotation.
These changes in distance can cause variations in the magnetic flux
sensed by a magnetostrictive torque sensor that are independent of
applied torque. Consequently, torque measurements acquired by
magnetostrictive torque sensors based upon sensed magnetic flux can
deviate from actual torque on a shaft.
SUMMARY
In general, systems and methods are provided for gap compensation
of magnetostrictive sensors, such as torque sensors.
In one embodiment, a magnetostrictive sensor is provided and it can
include a sensor head including a driving pole, two magnetic
sensors coupled to respective sensing poles, and a proximity coil.
The driving pole can have a driving coil coupled thereto that can
be configured to generate magnetic fluxes in response to a driving
current. The two magnetic sensors can each be configured to output
a first signal based at least upon first magnetic fluxes and second
magnetic fluxes sensed by the two magnetic sensors. The first
sensed magnetic fluxes can result from interaction of the generated
magnetic fluxes with a target, a gap between the sensor head and
the target, and the two sensing poles and the second sensed
magnetic fluxes resulting from interaction of the generated
magnetic fluxes with the gap. The proximity coil can be coupled to
the driving pole and it can be configured to output a second signal
based at least upon the first magnetic fluxes, the second sensed
magnetic fluxes, and third magnetic fluxes sensed by the proximity
coil. The third magnetic fluxes can result from interaction of the
generated magnetic fluxes with the gap.
In another embodiment, the sensor can include a controller in
electrical communication with the sensor head. The controller can
be configured to receive the first signals and the second signal,
determine a force applied to the target based upon the first
signals, determine the gap based upon the first signals and the
second signal, and adjust the force determined from the first
signals based upon the gap determined from the first signals and
the second signal.
In another embodiment, the force can be a torque.
In another embodiment, the two magnetic sensors can be arranged
approximately symmetrically with respect to the driving pole.
In another embodiment, the third sensed magnetic flux can be
approximately independent of electromagnetic properties of the
target.
In another embodiment, the second and third magnetic fluxes can
avoid impinging the target.
Methods for measuring proximity of a target are also provided. In
one embodiment, the method can include generating magnetic fluxes
that extend through a first region, a second region, and a third
region, the first region including a target, a pair of first
sensors, and a second sensor, the second region including the pair
of first sensors and the second sensor, and the third region
including the second sensor, measuring, by the pair of first
sensors, a combination of the first magnetic fluxes resulting from
interaction of the generated magnetic fluxes and the target and
second magnetic fluxes resulting from interaction of the generated
magnetic fluxes and a gap between the second sensor and the target
and measuring, by the second sensor, a combination of the first
magnetic fluxes, the second magnetic fluxes, and third magnetic
fluxes, the third magnetic fluxes resulting from interaction of the
generated magnetic fluxes and the gap.
In one embodiment, the method can also include determining the
third magnetic fluxes based upon combination of the first and
second magnetic fluxes measured by the pair of first sensors and
the first, second, and third magnetic fluxes measured by the second
sensor and determining the gap based upon the third magnetic
fluxes.
In another embodiment, the third magnetic flux can be approximately
independent of electromagnetic properties of the target.
In another embodiment, the second and third magnetic fluxes can
avoid impinging the target.
In another embodiment, each of the first and second sensors can be
inductive sensors configured to output a signal based upon magnetic
fields respectively extending therethrough.
In another embodiment, the pair of first sensors can be positioned
approximately symmetrically with respect to a source of the
generated magnetic flux.
Methods for compensating torque measurements for gap variations are
also provided. In one embodiment, the method can include generating
magnetic fluxes with a driving coil coupled to a driving pole of a
magnetostrictive torque sensor, outputting, by two magnetic sensors
coupled to respective sensing poles of the magnetostrictive sensor,
first signals based at least upon first magnetic fluxes and second
magnetic fluxes sensed by the two magnetic sensors, where the first
sensed magnetic fluxes can result from interaction of the generated
magnetic fluxes with a target, a gap between the magnetostrictive
torque sensor and the target, and the two sensing poles and the
second sensed magnetic fluxes can result from interaction of the
generated magnetic fluxes with the gap and the two sensing poles,
and outputting, by a proximity coil coupled to the driving pole, a
second signal based at least upon a combination of the first
magnetic fluxes, the second sensed magnetic fluxes, and third
magnetic fluxes sensed by the proximity coil, the third magnetic
fluxes can result from interaction of the generated magnetic fluxes
with the gap.
In one embodiment, the method can also include determining a torque
applied to the target based upon the first signals, determining the
gap based upon the first signals and the second signal, and
adjusting the torque determined from the first signals based upon
the gap determined from the first signals and the second
signal.
In another embodiment, the force can be a torque.
In another embodiment, the two magnetic sensors can be arranged
approximately symmetrically with respect to the driving pole.
In another embodiment, the third sensed magnetic flux can result
from interaction of the generated magnetic flux with the gap
only.
In another embodiment, the second and third magnetic fluxes can
avoid impinging the target.
DESCRIPTION OF DRAWINGS
These and other features will be more readily understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
FIG. 1 is a diagram illustrating one exemplary embodiment of an
operating environment including a magnetostrictive torque sensor
having a sensor head including a torque sensor and a proximity
sensor;
FIG. 2 is a side cross-sectional view of one exemplary embodiment
of a magnetostrictive torque sensor of FIG. 1 including a sensor
head having a core, a driving coil, two or more magnetic sensors,
and a proximity sensor;
FIG. 3 is a side cross-sectional view of the sensor head of FIG. 2
illustrating the spatial distribution magnetic flux generated by
driving coil;
FIG. 4 is a top view of an exemplary embodiment of a core of the
magnetostrictive torque sensor of FIG. 2; and
FIG. 5 is a flow diagram illustrating an exemplary embodiment of a
method for measuring torque and proximity of a target.
It is noted that the drawings are not necessarily to scale. The
drawings are intended to depict only typical aspects of the subject
matter disclosed herein, and therefore should not be considered as
limiting the scope of the disclosure. Those skilled in the art will
understand that the systems, devices, and methods specifically
described herein and illustrated in the accompanying drawings are
non-limiting exemplary embodiments and that the scope of the
present invention is defined solely by the claims.
DETAILED DESCRIPTION
Certain exemplary embodiments will now be described to provide an
overview of the principles of the structure, function, manufacture,
and use of the systems, devices, and methods disclosed herein. One
or more examples of these embodiments are illustrated in the
accompanying drawings. The features illustrated or described in
connection with one exemplary embodiment can be combined with the
features of other embodiments. Such modifications and variations
are intended to be included within the scope of the present
invention. Further, in the present disclosure, like-named
components of the embodiments generally have similar features, and
thus within a particular embodiment each feature of each like-named
component is not necessarily fully elaborated upon.
Magnetostrictive sensors, such as torque sensors, can include a
driving element that generates a magnetic flux and a sensing
element that measures the magnetic flux as it interacts with a
target (e.g., a rotating machine shaft) in order to determine
torque applied to the shaft. In some instances, the magnetic flux
sensed by the sensing element can be highly sensitive to changes in
the distance or gap from the target, and these gap variations can
introduce error into torque measurements determined from the sensed
magnetic flux. To improve the quality of torque measurements,
changes in the gap can be measured to compensate torque
measurements for gap variations. As an example, non-contact
proximity sensors can be used to determine the gap from
measurements of the magnetic flux generated by a magnetorestrictive
sensor. However, the accuracy of gap measurements acquired by these
non-contact proximity sensors can be compromised by changes in
electromagnetic properties of the target that cause sensed magnetic
fields to vary independently of the gap. Accordingly, improved gap
compensation measurements that isolate changes in measured magnetic
flux due to gap changes from changes in measured magnetic flux due
to electromagnetic characteristics of the target are provided for
use with magnetorestrictive torque sensors to enhance the accuracy
of torque measurements.
Embodiments of sensing systems and corresponding methods for
measuring torque of rotating machine components are discussed
herein. However, embodiments of the disclosure can be employed to
measure other forces applied to rotating or stationary machine
components without limit.
FIG. 1 illustrates one exemplary embodiment of an operating
environment 100 containing a gap compensated torque sensing system
102 and a target 104. The gap compensated torque sensing system 102
can be a magnetostrictive torque sensing system including a sensor
head 106, a torque sensor 110, a proximity sensor 112, and a
controller 114. The torque sensor 110 can be positioned within the
sensor head 106 and it can be configured to generate first signals
110s representative of torque applied to a selected portion of the
target 104. The proximity sensor 112 can also be positioned within
the sensor head 106 and it can be configured to generate second
signals 112s representative of a gap G between itself and the
selected portion of the target 104.
In use, the sensor head 106 can be positioned proximate to the
target 104 for acquiring torque and gap measurements. The
controller 114 can be configured to receive the first and second
signals 110s, 112s and it can determine a torque applied to the
selected portion of the target 104. The controller 114 can also
measure a gap G that is approximately independent of variations in
the electromagnetic properties of the target 104. From the first
signals 110s and the measured gap G, the controller 114 can adjust
the torque determined by the torque sensor 110 to compensate for
changes in the gap G (e.g., due to vibration and/or geometry
variations of the target). In this manner, the accuracy of the
torque measurements can be increased.
In certain embodiments, the sensor head 106 can be coupled to a
frame or other stationary fixture (not shown) to position the
sensor head 106 at a desired orientation and/or position with
respect to the target 104. In other embodiments, the torque and gap
measurements can be acquired from the target 104 while the target
104 is rotating (e.g., about a longitudinal axis A) or while the
target is stationary. Other embodiments are within the scope of the
disclosed subject matter.
FIG. 2 is a side cross-sectional view of one exemplary embodiment
of a gap compensated torque sensing system 200 that includes a
sensor head 202 in electrical communication with a controller 204.
The sensor head 202 can form a housing 206 that contains a torque
sensor including a core 210, a driving coil 212, and two or more
magnetic sensors (e.g., sensing coils 214a, 214b). The sensor head
202 can also include a proximity sensor including a proximity coil
216. As discussed in greater detail below, the torque sensor can be
configured to measure torque applied to a selected portion 220 of a
target 222 (e.g., a portion of the target 222 positioned opposite
the sensor head 202). The proximity sensor can be configured to
measure a gap 224 between the sensor head 202 (e.g., a distal end
206d of the housing 206) and the selected portion 220 of the target
222 concurrently with the torque measurements acquired by the
torque sensor.
The target 222 can be a component of any machine or equipment 226
that is configured to rotate. Examples of rotating components can
include, but are not limited to, shafts and rotors. Examples of
machines and equipment 226 incorporating rotating components can
include, but are not limited to, turbomachines (e.g., turbine
engines, compressors, pumps, and combinations thereof), generators,
combustion engines, and combinations thereof. Force or load can be
applied to the target 222 by a driver 230 (e.g., a reciprocating
engine, a combustion engine, a turbine engine, an electrical motor,
etc.) to enable the target 222 to rotate and drive a load. The
target 222 can be formed from materials including, but not limited
to, ferromagnetic materials such as iron, steel, nickel, cobalt,
and alloys thereof. In certain embodiments, the target 222 can be
non-magnetized. In other embodiments, the target 222 can be
magnetized.
The core 210 can include a base 232 and at least three elongated
poles 234, 236a, 236b. The poles 234, 236a, 236b can extend
outwards from the base 232 and they can be separated from one
another by a selected distance. The core 210 can be formed from any
ferromagnetic material. Examples can include, but are not limited
to, iron, steel, nickel, cobalt, and alloys thereof. One of the
poles 234 can be a driving pole to which the driving coil 212 is
wrapped around. The poles 236a, 236b can be sensing poles to which
the sensing coils 214a, 214b are wrapped around. In certain
embodiments, the sensing poles 236a, 236b can be positioned
approximately symmetrically about the driving pole 234.
The driving coil 212 and the sensing coils 214a, 214b can each be
in electrical communication with the controller 204. As shown in
FIG. 2, the controller 204 can be electrically coupled to an
excitation source ES 240 by wired or wireless connections. Wireless
communication devices, such as radio frequency (RF) transmitters,
can be integrated with the controller 204 to transmit the signals
to an RF receiver integrated with the excitation source ES 240. As
also shown in FIG. 2, the controller 204 can be positioned remotely
from the sensor head 202. However, in alternative embodiments (not
shown), the controller 204 can be positioned within the sensor head
202.
A power source 242 (e.g., electrical outlet, electrical generator,
battery, etc.) can provide power to the controller 204 and the
excitation source ES 240. The excitation source ES 240 can be
configured to deliver a driving current 244 (e.g., an AC current)
to the driving coil 212 and the controller 204 can be configured to
control characteristics of the driving current 244 delivered to the
driving coil 212 (e.g., frequency, amplitude, etc.) by the
excitation source ES 240. The controller 204 can be any computing
device employing a general purpose or application-specific
processor 246. In either case, the controller 204 can include
memory 250 for storing instructions related to characteristics of
the driving current 244, such as frequency, amplitude, and
combinations thereof. The memory 250 can also include instructions
and algorithms for employing sensor signals (e.g., torque signals
248a, 248b and proximity signal 252) to determine torque
measurements, improved gap measurements, and compensating torque
measurements based on the improved torque measurements, as
discussed in greater detail below. The processor 246 can include
one or more processing devices, and the memory 250 can include one
or more tangible, non-transitory, machine-readable media
collectively storing instructions executable by the processor 246
to perform the methods and control actions described herein.
The driving current 244 can pass through the driving coil 212 to
generate magnetic fluxes 254a, 254b. At least a portion of the
magnetic fluxes 254a, 254b can permeate the core 210 and the target
222, pass through the sensing coils 214a, 214b and the proximity
coil 216, and return to the driving coil 212 via the core 210
(e.g., the sensing poles 236a, 236b). In this manner, a magnetic
loop can be formed through the torque sensor and the target 222. As
discussed in greater detail below, additional magnetic fluxes
having spatial distributions different from the magnetic fluxes
254a, 254b can also be present.
The sensing coils 214a, 214b can be used to measure magnetic fluxes
254a, 254b exiting the target 222. Because force (e.g.,
compression, tension, torsion, etc.) applied to the target 222 can
change the magnetic permeability of the target 222, magnetic fluxes
254a, 254b sensed by the sensing coils 214a, 214b can change. Thus,
the torque applied to the target 222 can be determined based on
changes in the magnetic fluxes 254a, 254b sensed by the sensing
coils 214a, 214b relative to the magnetic fluxes 254a, 254b
generated by the driving coil 212. The sensing coils 214a, 214b can
be configured to transmit torque signals 248a, 248b indicative of
the changes (e.g., differences) in the magnetic fluxes 254a, 254b
to the controller 204. Under circumstances where the sensing poles
236a, 236b are positioned symmetrically with respect to the driving
pole 234, the magnetic fluxes 254a, 254b sensed by the sensing
coils 214a, 214b can be the same, resulting in the generated torque
signals 248a, 248b also being the same.
In an alternative embodiment, the magnetic fluxes 254a, 254b
exiting the target 222 can be measured by secondary magnetic
sensors (not shown) other than the sensing coils 214a, 214b. The
secondary magnetic sensors can be configured similarly to the
sensing coils 214a, 214b and they can transmit torque signals 248a,
248b indicative of the changes (e.g., differences) in the magnetic
fluxes 254a, 254b to the controller 204. In contrast to the sensing
coils 214a, 214b, the secondary magnetic sensors can be located off
of the sensing poles 236a, 236b and instead coupled to the sensing
poles 236a, 236b by a coupling formed from a material that does not
interfere with the magnetic fluxes 254a, 254b. That is, the
secondary magnetic sensors can be coils or any other magnetic
sensor capable of measuring the magnetic fluxes 254a, 254b exiting
the target 222. The position of the secondary magnetic sensors can
be approximately symmetric with respect to the driving pole
234.
The torque signals 248a, 248b can be communicated by wired or
wireless connections to the controller 204 (e.g., receiver 256). As
an example, wireless communication devices, such as RF
transmitters, can be integrated with the sensor head 202 (e.g.,
proximate to the sensing coil 214) to transmit the signals to an RF
receiver integrated with the controller 204. The receiver 256 can
include electronic components (e.g., amplifiers, filters, etc.)
that can condition the torque signals 248a, 248b before
transmitting them to the processor 246 (e.g., 260). In other
embodiments, the torque signals 248a, 248b can be conditioned after
being processed by the processor 246.
Upon receipt of the torque signals 248a, 248b from the sensing
coils 214a, 214b, the processor 246 can process the torque signals
248a, 248b to estimate the torque applied to the target 222. That
is, the processor 246 can execute pre-stored and/or user-defined
algorithms in the memory 250 to calculate the magnitude of the
torque applied to the target 222 based on the characteristics of
the target 222, the sensor head 202, and the driving current
244.
As discussed above, the torque measurements can be affected by the
gap 224. Thus, torque measurements determined for the target 222
based upon magnetic fluxes 254a, 254b sensed by the torque sensor
can deviate from the actual torque applied to the target 222. To
address this issue, the gap 224 can be measured by the proximity
sensor (e.g., the proximity coil 216) and it can be used to adjust
the torque measurements to account for variations in the gap 224.
In this manner, the proximity sensor can improve the accuracy of
the torque measurements and enable better control of the machine or
equipment 226 incorporating the target 222.
The position of the proximity coil 216 relative to the target 222
can be selected to facilitate both the torque measurements acquired
by the torque sensor and the gap measurements acquired by the
proximity coil 216. As shown in FIG. 2, the proximity sensor can be
an inductive proximity sensor and the proximity coil 216 can be
positioned on the driving pole 234. In certain embodiments, the
proximity coil 216 can be positioned distally of the driving coil
212 on the driving pole 234. So positioned, the proximity coil 216
can act as an inductive pick-up coil, transmitting proximity
signals 252 representative of the gap 224 based upon changes in the
magnetic fluxes 254a, 254b.
The proximity signal 252 can be communicated by wired or wireless
connections to the controller 204 (e.g., receiver 256). As an
example, wireless communication devices, such as RF transmitters,
can be integrated with the sensor head 202 (e.g., proximate to the
sensing coil 214) to transmit the signals to an RF receiver
integrated with the controller 204. The receiver 256 can include
electronic components (e.g., amplifiers, filters, etc.) that can
condition the proximity signal 252 before transmitting the
proximity signal 252 to the processor 246. In other embodiments,
the torque signal 248 can be conditioned after being processed by
the processor 246.
Upon receipt of the proximity signal 252 from the proximity coil
216, the processor 246 can process the proximity signal 252 and
determine the gap 224. That is, the processor 246 can execute
pre-stored and/or user-defined algorithms in the memory 250 to
calculate the magnitude of the gap 224. However, employing the
proximity signal 252 alone to determine the gap 224 can compromise
the accuracy of the gap measurement. As discussed above, the
magnetic fluxes 254a, 254b can be influenced both by the
electromagnetic properties of the target 222 and the gap 224. In
one aspect, the electromagnetic properties of the target 222 can
vary due to applied forces (e.g., torque, bending, thrust, etc.).
In another aspect, electromagnetic properties of the target 222 can
vary due to inhomogeneity in the chemical composition of the target
222, that is, electromagnetic runout. These inhomogeneities can
arise from the formation of rust or other chemical reactions at the
surface of the target 222.
To address this issue, the torque signals 248a, 248b can be
combined with the proximity signal 252 to provide an adjusted or
improved proximity signal that can be independent of the
electromagnetic properties of the target 222 and it can more
accurately represent the gap 224 than the proximity signal 252. As
discussed in detail below, this adjustment can be accomplished due
to symmetry of the sensing coils 214a, 214b and spatial
distribution of magnetic fluxes generated by the driving coil
212.
FIG. 3 shows the sensor head 202, illustrating the magnetic fluxes
254a, 254b in greater detail. The housing 206 is omitted for
clarity. As shown, the magnetic fluxes 254a, 254b can be
partitioned into different components (e.g., .PHI..sub.1,
.PHI.'.sub.1, .PHI..sub.2, .PHI.'.sub.2, .PHI..sub.3, and
.PHI.'.sub.3) based upon their spatial distribution. Each of the
magnetic flux components can be dependent upon the electromagnetic
properties of the target 222, interchangeably referred to below as
.delta., the gap 224, interchangeably referred to below as g, or
both. .delta. can represent the effects of stress induced by
torque, varying magnetic permeability, and/or electrical
conductivity (e.g., electromagnetic runout).
Magnetic fluxes .PHI..sub.1 and .PHI.'.sub.1 can form loops passing
through the core 210 (e.g., the base 232, the driving pole 234, and
the sensing poles 236a, 236b, respectively), the gap 224, and the
target 222. As a result, the magnetic fluxes .PHI..sub.1 and
.PHI.'.sub.1 can each be a function of both the electromagnetic
properties of the target 222 and the gap 224. Symbolically, the
magnetic fluxes .PHI..sub.1 and .PHI.'.sub.1 can be represented by
the equations .PHI..sub.1=f.sub.1(.delta., g) and
.PHI.'.sub.1=f'.sub.1(.delta., g), where f.sub.1 and f'.sub.1 are
functional dependences of .PHI..sub.1 and .PHI.'.sub.1 on g,
respectively.
Magnetic fluxes .PHI..sub.2 and .PHI.'.sub.2 can form loops passing
through the core 210 (e.g., the base 232, the driving pole 234, and
the sensing poles 236a, 236b, respectively) and the gap 224 but not
the target 222. Thus, the magnetic fluxes .PHI..sub.2 and
.PHI.'.sub.2 have a different spatial distribution from the
magnetic fluxes .PHI..sub.1 and .PHI.'.sub.1, which causes the
magnetic fluxes .PHI..sub.2 and .PHI.'.sub.2 to be dependent only
on the value of the gap 224. Symbolically, the magnetic fluxes
.PHI..sub.2 and .PHI.'.sub.2 can be represented by the equations
.PHI..sub.2=f.sub.2(g) and .PHI..sub.2=f'.sub.2(g), where f.sub.2
and f'.sub.2 are the functional dependences of .PHI..sub.2 and
.PHI.'.sub.2 on g, respectively.
Magnetic fluxes .PHI..sub.3 and .PHI.'.sub.3 can form loops passing
through a portion of the core 210 (e.g., the base 232 and the
driving pole 234) and the gap 224 but not the sensing poles 236a,
236b or the target 222. As a result, the magnetic fluxes
.PHI..sub.3 and .PHI.'.sub.3 can be functions only of g. However,
because the magnetic fluxes .PHI..sub.3 and .PHI.'.sub.3 have a
different spatial distribution from the magnetic fluxes .PHI..sub.2
and .PHI.'.sub.2, they adopt different values. Symbolically, the
magnetic flux .PHI..sub.3 can be represented by the equations
.PHI..sub.3=f.sub.3(g) and .PHI.'.sub.3=f.sub.3(g), where f.sub.3
and f'.sub.3 are the functional dependence of .PHI..sub.3 and
.PHI.'.sub.3 on g.
Owing to its position on the sensing pole 236a, the torque signal
248a can result from voltage induced within the sensing coil 214a
by the magnetic fluxes .PHI..sub.1 and .PHI..sub.2. Thus, the
torque signal 248a, referred to as U.sub.1sense below, can be
represented symbolically as a function that is proportional to sum
of the magnetic fluxes .PHI..sub.1 and .PHI..sub.2, given by
U.sub.1sense=a(.PHI..sub.1+.PHI..sub.2), where a is a
proportionality constant.
Owing to its position on the sensing pole 236b, torque signal 248b
can result from voltage induced within the sensing coil 214b by the
magnetic fluxes .PHI.'.sub.1 and .PHI.'.sub.2. Thus, the torque
signal 248b, referred to as U.sub.2sense below, can be represented
symbolically as a function that is proportional to sum of the
magnetic fluxes .PHI.'.sub.1 and .PHI.'.sub.2, given by
U.sub.2sense=a(.PHI.'.sub.1+.PHI.'.sub.2).
Owing to its position on the driving pole 234, the proximity signal
252 can result from voltage induced within the proximity coil 216
by the magnetic fluxes .PHI..sub.1, .PHI.'.sub.1, .PHI..sub.2,
.PHI.'.sub.2, .PHI..sub.3, and .PHI.'.sub.3. Thus, the proximity
signal 252, referred to as U.sub.prox below, can be represented
symbolically as a function that is proportional to sum of the
magnetic fluxes .PHI..sub.1, .PHI.'.sub.1, .PHI..sub.2,
.PHI.'.sub.2, .PHI..sub.3 and .PHI.'.sub.3, given by
U.sub.prox=b(.PHI..sub.1+.PHI.'.sub.1+.PHI..sub.2+.PHI.'.sub.2+.-
PHI..sub.3+.PHI..sub.3), where b is a proportionality constant.
It can be assumed that U.sub.1sense is approximately equal to
U.sub.2sense, owing to the symmetry of the sensing poles 236a, 236b
with respect to the driving pole 234. Additionally, the
proportionality constants a and b can be set to be equal, either
numerically or by electronics of the torque sensor and the
proximity sensor.
Based upon these assumptions, the controller 204 (e.g., the
processor 246) can determine an adjusted or improved proximity
signal U.sub.prox.sub._.sub.imp that depends only upon g using the
torque signals 248a, 248b and the proximity signal 252. As an
example, the processor 246 can subtract U.sub.prox (the proximity
signal 252) from the sum of U.sub.1sense and U.sub.2sense (the sum
of torque signals 248a, 248b) That is, the controller 204 can
combine U.sub.1sense, U.sub.2sense, and U.sub.prox in such a manner
that functions dependent upon 6 are eliminated, leaving only
functions dependent upon g.
U.sub.prox.sub._.sub.imp=U.sub.1sense+U.sub.2sense-U.sub.prox
U.sub.prox.sub._.sub.imp=a(.PHI..sub.1+.PHI..sub.2)+a(.PHI.'.sub.1+.PHI.'-
.sub.2)-b(.PHI..sub.1+.PHI.'.sub.1+.PHI..sub.2+.PHI.'.sub.2+.PHI..sub.3+.P-
HI.'.sub.3)
U.sub.prox.sub._.sub.imp=a(.PHI..sub.1+.PHI..sub.2)+a(.PHI.'.sub.1+.PHI.'-
.sub.2)-a(.PHI..sub.1+.PHI.'.sub.1+.PHI..sub.2+.PHI.'.sub.2+.PHI..sub.3+.P-
HI.'.sub.3)
U.sub.prox.sub._.sub.imp=a(.PHI..sub.3+.PHI.'.sub.3)=f.sub.4(g)
Upon determining the improved proximity signal
U.sub.prox.sub._.sub.imp, the processor 246 can execute pre-stored
and/or user-defined algorithms in the memory 250 to process the
improved proximity signal U.sub.prox.sub._.sub.imp and the torque
signals 248a, 248b and determine a gap compensated torque
measurement that is improved over a measurement of the torque based
only upon the torque signals 248a, 248b or a measurement of the
torque compensated by the proximity signal 252.
While the sensor head of FIG. 2 illustrates a gap compensated
torque sensing system 200 including a core 210 having the two
sensing poles 236a, 236b, alternative embodiments of the core can
include any different numbers of sensing poles (e.g., 2, 3, 4, 5,
6, 7, 8, 9, 10), provided that at least two of the sensing poles
are arranged symmetrically with respect to a driving pole and
include sensing coils to facilitate determination of the improved
proximity signal U.sub.prox.sub._.sub.imp.
As an example, FIG. 4 is a top view of an exemplary embodiment of a
core 400 suitable for use with the gap compensated torque sensing
system 200. As shown, the core 400 can include a cross axis yoke
402 having a cross yoke portion 404 and four bases 406a, 406b,
406c, 406d. The bases 406a, 406b, 406c, 406d can extend radially
outward in a plane from the cross yoke portion 404 in any
configuration and for any length that enables each to operate as
described herein. The bases 406a, 406b, 406c, 406d can be angularly
spaced apart by an angle ranging from about 10 degrees to 135
degrees (e.g., 10 degrees, 20 degrees, 30 degrees, 40 degrees, 45
degrees, 60 degrees, 75 degrees, 90 degrees, 120 degrees, 135
degrees, or any combination thereof). As shown in FIG. 4, the bases
406a, 406b, 406c, 406d can be angularly spaced apart by
approximately 90 degrees. Additional embodiments of the sensor head
and the torque sensor are discussed in U.S. Pat. No. 9,618,408, the
entirety of which is hereby incorporated by reference.
FIG. 5 is a flow diagram illustrating an exemplary embodiment of a
method 500 for measuring force (e.g., torque) and proximity of a
target (e.g., 222) using any of the sensing systems discussed
herein. The method 500 is described below in connection with the
gap compensated torque sensing system 200 of FIG. 2. However, the
method 500 is not limited to use with the gap compensated torque
sensing system 200 and it can be employed with any magnetostrictive
torque sensor. In certain aspects, embodiments of the method 500
can include greater or fewer operations than illustrated in FIG. 5
and can be performed in a different order than illustrated in FIG.
5.
In operation 502, a gap compensated torque sensing system (e.g.,
200) can be positioned proximate to a target (e.g., 222). As
discussed above, the gap compensated torque sensing system 200 can
include the torque sensor and the proximity sensor.
In operation 504, magnetic fluxes can be generated by the gap
compensated torque sensing system 200 (e.g., by driving coil 212).
A first portion of the generated magnetic fluxes can be directed
through each of the driving pole 234, the sensing poles 236, the
gap 224, and the target 222 (e.g., .PHI..sub.1 and .PHI..sub.2). A
second portion of the generated magnetic fluxes can be directed
through the driving pole 234, the sensing poles 236, and the gap
224, and but not the target 222 (e.g., .PHI..sub.2 and
.PHI.'.sub.2). A third portion of the generated magnetic fluxes can
be directed through the driving pole 234 and the gap 224 but not
the sensing poles 236a, 236b or the target 222 (e.g., .PHI..sub.3
and .PHI.'.sub.3).
In operation 506, magnetic fluxes representing a net interaction of
the generated magnetic fluxes with the target 222 and/or the gap
224, can be sensed by the torque sensor (e.g., the sensing coils
214a, 214b) and/or the proximity sensor (e.g., proximity coil 216).
As an example, first magnetic fluxes (e.g., .PHI..sub.1 and
.PHI.'.sub.1) can be sensed by the torque sensor and the proximity
sensor and they can represent net interactions of the generated
magnetic flux with the target 222 and the gap 224. Second magnetic
fluxes (e.g., .PHI..sub.2 and .PHI.'.sub.2) can be sensed by the
torque sensor and the proximity sensor and they can represent net
interactions of the generated magnetic flux with the gap 224 alone.
Third magnetic fluxes (e.g., .PHI..sub.3 and .PHI.'.sub.3) can be
sensed by the proximity sensor and they can represent net
interactions of the third portion of the first magnetic flux with
the gap 224 alone that is sensed by the proximity sensor (e.g.,
proximity coil 216) but not sensed by the torque sensor.
In operation 510, first signals (e.g., torque signals 248a, 248b)
can be output by the torque sensor based upon the first and second
magnetic fluxes sensed by the torque sensor.
In operation 512, second signal (e.g., proximity signal 252) can be
output by the proximity sensor based upon the first, second, and
third magnetic fluxes measured by the proximity sensor. The second
signals can depend upon both a gap between a selected portion of
the target 222 (e.g., 220) and electromagnetic properties of the
target 222.
In operation 514, torque applied to the target 222 can be
determined from the first signals 248a, 248b.
In operation 516, an improved gap measurement can be determined
from the first signals 248a, 248b and the second signal 252. The
improved gap measurement can be approximately independent of the
electromagnetic properties of the target 222. That is, the improved
gap measurement can be substantially dependent only upon the gap
224.
In operation 520, a gap compensated torque applied to the target
222 can be determined based upon the torque estimate determined
from the first signals and the improved gap measurement.
Exemplary technical effects of the methods, systems, and devices
described herein include, by way of non-limiting example, improved
gap estimation for compensation of torque measurements. Integration
of one or more proximity sensors into a force sensing system (e.g.,
a torque sensing system) can reduce error in torque measurements
due to electromagnetic runout of the target and/or loads applied to
the target. Without correcting the proximity signal, the residual
error due to electromagnetic runout of the target and any load
applied to the target can be as high as about .+-.40% of the
full-scale torque signal. For context, many torque sensing
applications can require residual errors of about .+-.5% of the
full-scale torque signal. Thus, the ability to provide an improved
proximity signal can help to realize this desired accuracy.
The subject matter described herein can be implemented in analog
electronic circuitry, digital electronic circuitry, and/or in
computer software, firmware, or hardware, including the structural
means disclosed in this specification and structural equivalents
thereof, or in combinations of them. The subject matter described
herein can be implemented as one or more computer program products,
such as one or more computer programs tangibly embodied in an
information carrier (e.g., in a machine-readable storage device),
or embodied in a propagated signal, for execution by, or to control
the operation of, data processing apparatus (e.g., a programmable
processor, a computer, or multiple computers). A computer program
(also known as a program, software, software application, or code)
can be written in any form of programming language, including
compiled or interpreted languages, and it can be deployed in any
form, including as a stand-alone program or as a module, component,
subroutine, or other unit suitable for use in a computing
environment. A computer program does not necessarily correspond to
a file. A program can be stored in a portion of a file that holds
other programs or data, in a single file dedicated to the program
in question, or in multiple coordinated files (e.g., files that
store one or more modules, sub-programs, or portions of code). A
computer program can be deployed to be executed on one computer or
on multiple computers at one site or distributed across multiple
sites and interconnected by a communication network.
The processes and logic flows described in this specification,
including the method steps of the subject matter described herein,
can be performed by one or more programmable processors executing
one or more computer programs to perform functions of the subject
matter described herein by operating on input data and generating
output. The processes and logic flows can also be performed by, and
apparatus of the subject matter described herein can be implemented
as, special purpose logic circuitry, e.g., an FPGA (field
programmable gate array) or an ASIC (application-specific
integrated circuit).
Processors suitable for the execution of a computer program
include, by way of example, both general and special purpose
microprocessors, and any one or more processor of any kind of
digital computer. Generally, a processor will receive instructions
and data from a read-only memory or a random access memory or both.
The essential elements of a computer are a processor for executing
instructions and one or more memory devices for storing
instructions and data. Generally, a computer will also include, or
be operatively coupled to receive data from or transfer data to, or
both, one or more mass storage devices for storing data, e.g.,
magnetic, magneto-optical disks, or optical disks. Information
carriers suitable for embodying computer program instructions and
data include all forms of non-volatile memory, including by way of
example semiconductor memory devices, (e.g., EPROM, EEPROM, and
flash memory devices); magnetic disks, (e.g., internal hard disks
or removable disks); magneto-optical disks; and optical disks
(e.g., CD and DVD disks). The processor and the memory can be
supplemented by, or incorporated in, special purpose logic
circuitry.
To provide for interaction with a user, the subject matter
described herein can be implemented on a computer having a display
device, e.g., a CRT (cathode ray tube) or LCD (liquid crystal
display) monitor, for displaying information to the user and a
keyboard and a pointing device, (e.g., a mouse or a trackball), by
which the user can provide input to the computer. Other kinds of
devices can be used to provide for interaction with a user as well.
For example, feedback provided to the user can be any form of
sensory feedback, (e.g., visual feedback, auditory feedback, or
tactile feedback), and input from the user can be received in any
form, including acoustic, speech, or tactile input.
The techniques described herein can be implemented using one or
more modules. As used herein, the term "module" refers to computing
software, firmware, hardware, and/or various combinations thereof.
At a minimum, however, modules are not to be interpreted as
software that is not implemented on hardware, firmware, or recorded
on a non-transitory processor readable recordable storage medium
(i.e., modules are not software per se). Indeed "module" is to be
interpreted to always include at least some physical,
non-transitory hardware such as a part of a processor or computer.
Two different modules can share the same physical hardware (e.g.,
two different modules can use the same processor and network
interface). The modules described herein can be combined,
integrated, separated, and/or duplicated to support various
applications. Also, a function described herein as being performed
at a particular module can be performed at one or more other
modules and/or by one or more other devices instead of or in
addition to the function performed at the particular module.
Further, the modules can be implemented across multiple devices
and/or other components local or remote to one another.
Additionally, the modules can be moved from one device and added to
another device, and/or can be included in both devices.
The subject matter described herein can be implemented in a
computing system that includes a back-end component (e.g., a data
server), a middleware component (e.g., an application server), or a
front-end component (e.g., a client computer having a graphical
user interface or a web browser through which a user can interact
with an implementation of the subject matter described herein), or
any combination of such back-end, middleware, and front-end
components. The components of the system can be interconnected by
any form or medium of digital data communication, e.g., a
communication network. Examples of communication networks include a
local area network ("LAN") and a wide area network ("WAN"), e.g.,
the Internet.
Approximating language, as used herein throughout the specification
and claims, may be applied to modify any quantitative
representation that could permissibly vary without resulting in a
change in the basic function to which it is related. Accordingly, a
value modified by a term or terms, such as "about,"
"approximately," and "substantially," are not to be limited to the
precise value specified. In at least some instances, the
approximating language may correspond to the precision of an
instrument for measuring the value. Here and throughout the
specification and claims, range limitations may be combined and/or
interchanged, such ranges are identified and include all the
sub-ranges contained therein unless context or language indicates
otherwise.
One skilled in the art will appreciate further features and
advantages of the invention based on the above-described
embodiments. Accordingly, the present application is not to be
limited by what has been particularly shown and described, except
as indicated by the appended claims. All publications and
references cited herein are expressly incorporated by reference in
their entirety.
* * * * *